If a channel condition between a base station and a UE is poor, a relay node (RN) may be installed between the base station and the UE to provide a radio channel having better channel conditions to the UE. An RN may also be installed in a cell edge region having a poor channel condition to provide a higher-speed data channel, extending a cell service region. Thus, the RN has been widely used to reduce radio dead zone in a wireless communication system.
While conventional relay schemes only employ a repeater function which merely amplifies signals, recent relay schemes have been developed into more intelligent forms. The RN technology is essential to increase the service coverage and improve throughput while reducing costs associated with increasing the number of base stations and maintenance costs of a backhaul network in a next generation mobile communication system. With the increasing development of RN technology, there is a need for such new wireless communication systems to support RNs used in the conventional wireless communication system.
In a 3rd Generation Partnership Project Long Term Evolution (3GPP LTE) system, as an RN has adopted a function to forward link connection between a base station and a User Equipment (UE), two links having different attributes have been respectively applied to uplink and downlink carrier frequency bands. A connection link set between a base station and a RN is defined as a backhaul link. Frequency Division Duplex (FDD) or Time Division Duplex (TDD) transmission using downlink resources is referred to as backhaul downlink and FDD or TDD transmission using uplink resources is referred to as backhaul uplink.
FIG. 1 illustrates a configuration of a relay backhaul link and a relay access link in a wireless communication system.
As shown in FIG. 1, the RN may receive information from a base station (or eNode B (eNB)) through a relay backhaul downlink and may transmit information to a base station through a relay backhaul uplink. The RN may transmit information to a UE through the relay access downlink and may receive information from a UE through the relay access uplink.
In the case where an LTE-Advanced (LTE-A) system, which has improved the LTE system which is a mobile communication system, supports an RN, a base station needs to feed an ACK/NACK back to the RN in response to uplink transmission to the base station from the RN. However, there have been no methods for transmitting an ACK/NACK feedback from a base station in response to uplink transmission from an RN in an LTE-A system and there also have been no designs and suggestions associated with channel allocation for ACK/NACK feedback. However, in the case where the LTE-A system supports an RN, there is a need to design a downlink ACK/NACK feedback from a base station to the RN and to design channels for the downlink ACK/NACK feedback.